Blower capacity requirements

Figure 4-60. Expander deliver capacity versus blower capacity requirements.

Fluidized-bed roasting accounts for most of the world zinc production today. Over the last 15 years, several zinc roasters have augmented their calcine production capacities with oxygen enrichment. These roasters typically encounter production increase limitations due to existing blower capacities, requirements for fluidization characteristics of the bed, and downstream gas-handling capacities. Oxygen enrichment provides roaster operators with a tool to increase roaster capacity in a cost-effective way. Several roaster plants utilize oxygen enrichment to improve calcine... 

A surface effect (air cushion) vehicle measures 10 ft by 20 ft and weighs 6000 lbf. The air is supplied by a blower mounted on top of the vehicle, which must supply sufficient power to lift the vehicle 1 in. off the ground. Calculate the required blower capacity in scfm (standard cubic feet per minute), and the horsepower of the motor required to drive the blower if it is 80% efficient. Neglect friction, and assume that the air is an ideal gas at 80°F with properties evaluated at an average pressure. 

The minimum positive pressure differential between the room and any adjacent area of less clean requirement should be 0.05 in. water (12 Pa), with all entryways closed. When the entryways are open, the blower capacity should be adequate to maintain an outward flow of air to minimize contamination migrating into the room. 

In the rotary blower, shown in Figure 5.2, gases are trapped in between two interlocking rotors which rotate in opposite directions. The blower requires no seal fluid. Because of the required clearances between the rotors of 0.025 to 0.25 mm (9.84x10 to 9.84x10 in), backflow reduces the blower capacity [3]. Also, overheating limits the pressure increase. 

Gas-moving Equipment. The principal types of equipment available for gas pumping are blowers, compressors, ejectors, fans, and vacuum pumps. The following is a general guide for selection of equipment based on pressure and capacity requirement ... 

Gas flow rates through the roasting, gas purification and acid plant sections are currently limited by the capacity of the existing KKK blower. The requirement to increase these flow rates upon expansion will need to be met. Four possible means of achieving this were indicated ... 

Examination of Table 9.1 shows that the air provided by the plant (7 = 50dC, Gs = 0.1 kg/s) underestimated the minimum requirement by a factor of 14. Even at a temperature of 125dC, the minimum flow required was still five times that actually provided. Clearly, a combination of both higher temperature and greater blower capacity would be required to meet the drying specifications. A reasonable recommendation would be for a flow rate of 1 kg/s at 125dC at the point of delivery. This provides a safety factor of 2 over the tabulated (GJ m of 0-49 kg/s. 

The LO-CAT II oxidizer vessel has been redesigned to provide better mass transfer and reduce the air blower head and capacity requirements. Unlike the vertical cylindrical vessels used in the LO-CAT design, the new LO-CAT II oxidizers are flat-bottomed, shorter, and rectangular in shape. A picture of the oxidizer box and air blowers installed in the Mobil LO-CAT II unit is shown in Figure 9-35. 

The steam balance in the plant shown in Figure 2 enables all pumps and blowers to be turbine-driven by high pressure steam from the boiler. The low pressure exhaust system is used in the reboiler of the recovery system and the condensate returns to the boiler. Although there is generally some excess power capacity in the high pressure steam for driving other equipment, eg, compressors in the carbon dioxide Hquefaction plant, all the steam produced by the boiler is condensed in the recovery system. This provides a weU-balanced plant ia which few external utiUties are required and combustion conditions can be controlled to maintain efficient operation. 

As shown in Figure 2.25, it is more efficient to use a backing pump combined with one or two roots blowers (Fig. 2.27). The backing pump requires only 40 m3/h capacity, combined with a roots pump of 200 m3/h. This system evacuates the 1000 L also in 8 min down to 0.01 mbar, but below 0.1 mbar the system has a capacity of 200 m3/h or 2.2 10 3 g/s at 0.05 mbar. Such a pumping system is preferable for freeze drying compared with a large two-stage pump alone. 

A cooling tower operates in the countercurrent mode as illustrated by Figure 5.13. Entering air has a 5% wet-bulb temperature of 65°F. Hot process water enters the tower at 118°F and cold water leaves at a 15° approach to the wet-bulb (i.e., at 80°F). The cross-sectional area of the tower is 676 ft2. Determine the number of transfer units (Ntu ) required to meet the process requirements. Air is supplied to the tower by a blower having a capacity of 250,000 cfm and the water loading is 1500 lb/(hr)(ft2). 

If a high pumping capacity is required in production freeze-drying plants, a single backing pump with two blowers in parallel (Figure 2.37) is an effective solution. 

Piston Compressors and Blowers.—The large quantities of air required for blast-furnaces and Bessemer converters are usually supplied by piston compressors of large capacity, driven either by steam or gas engines. Turbo-blowers directly driven by steam turbines, however, have been recently developed for this work. 

This project will identify the constraints that prevent existing fuel processors from reaching rated capacity in 30 seconds or less. A fundamental technical barrier is the thermal mass of the catalysts and stmctural materials. Reductions in thermal mass require improvements in catalyst materials and effective heat transfer. Other limiting factors are related to auxiliary equipment and process design, such as available gas blowers and burners, the fuel injection system, sensor response, and hot gas distribution within the processor. 

At the John Zink Company (Tulsa, OK), various flare designs are tested comprehensively to determine performance parameters such as flame stability, flame length, smokeless capacity, purge rate required, blower horsepower, or steam requirements for assisted flares, tip longevity, radiation, and noise. All relevant data are recorded for each test in a single record. The data acquisition system consists of three computers (see Figure 28.9) ... 

---